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Summary
The File interface provides information about -- and access to the contents of -- files.
These are generally retrieved from a FileList object returned as a result of a user selecting files using the <input>DataTransfer object, or from the mozGetAsFile() API on an HTMLCanvasElement.
The file reference can be saved when the form is submitted while the user is offline, so that the data can be retrieved and uploaded when the Internet connection is restored.
Properties
-
File.lastModifiedDateRead only -
The last modified
Dateof the file referenced by theFileobject. -
File.nameRead only -
The name of the file referenced by the
Fileobject. -
File.fileNameRead only Obsolete since Gecko 7.0 -
The name of the file referenced by the
Fileobject. -
File.fileSizeRead only Obsolete since Gecko 7.0 - The size of the referenced file in bytes.
Methods
-
File.getAsBinary()Obsolete since Gecko 7.0 - Returns a string containing the file's data in raw binary format.
-
File.getAsDataURL()Obsolete since Gecko 7.0 -
A string containing the file's data encoded as a
data:URL. -
File.getAsText(string encoding)Obsolete since Gecko 7.0 - Returns the file's contents as a string in which the file's data is interpreted as text using a given encoding.
The File interface also inherits methods from the Blob interface.
-
Blob.slice() -
Returns a new
Blobobject containing the data in the specified range of bytes of the sourceBlob.
Note: Be aware that the
slice() method has vendor prefixes on some browsers and versions: blob.mozSlice() for Firefox 12 and earlier and blob.webkitSlice() in Safari. An old version of the slice() method, without vendor prefixes, had different semantics, and is obsolete.Specifications
| Specification | Status | Comment |
|---|---|---|
| File API | Working Draft | Initial definition. |
Browser compatibility
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|
| Basic support | 13 | 3.0 (1.9) (non standard) 7.0 (7) (standard) |
10.0 | 16.0 | 6.0 |
| Feature | Android | Firefox Mobile (Gecko) | IE Phone | Opera Mobile | Safari Mobile |
|---|---|---|---|---|---|
| basic support | Not supported | 25 | Not supported | 11.1 | 6.0 |
Implementation notes
Gecko notes
- In Gecko, you can use this API from chrome code. See Using the DOM File API in chrome code for details.
- Starting in Gecko 6.0 (Firefox 6.0 / Thunderbird 6.0 / SeaMonkey 2.3), privileged code (such as extensions) can pass an
nsIFileobject to the DOMFileconstructor to specify the file to reference. - Starting in Gecko 8.0 (Firefox 8.0 / Thunderbird 8.0 / SeaMonkey 2.5), you can use
new Fileto createFileobjects from XPCOM component code instead of having to instantiate thensIDOMFileobject directly.